Mounting device for disk-shaped rotating tool

ABSTRACT

An annular retaining groove is formed on the inner circumferential portion of the disk-shaped rotating tool, and a ringlike cushioning member is fitted in this annular retaining groove so as to be partially exposed. Both sides of the inner circumferential portion of the disk-shaped rotating tool are held by first and second holding members through the annular cushioning member. An axial portion of the first holding member is engaged with an output shaft of an electric rotary machine so that the disk-shaped rotating tool is rotated through the first holding member by the output shaft.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a device for mounting a disk-shaped rotating tool such as a grinding disk and a circular saw to an output shaft of an electric rotary machine in the condition that the tool is held from both sides thereof under elastic pressure.

2. Description of the Related Art

A grinding disk mounted on an output shaft of an electric rotary machine is used for leveling of the plane surface of a concrete, building material, and stone material, etc. or for any other various operations such as chamfering, repairing of a building wall surface, and removing of a painted surface. During such operations, a large impact is applied to an operator. In a conventional grinding disk, such a large impact is directly transmitted to the operator, making the operations difficult and having a physically adverse effect on the operator due to vibrations.

To prevent such a physically adverse effect on the operator due to vibrations, Japanese Patent No. 3032530 has proposed a mounting structure such that a grinding disk is mounted through a shock absorbing ring having a cushion member to an output shaft of an electric rotary machine. In this mounting structure, the vibrations of the grinding disk during the operation are reduced by the cushion member and transmitted to the electric rotary machine, so that the burden on the operator due to the vibrations can be reduced.

However, in this mounting structure, an annular groove for retaining the cushion member is formed on the shock absorbing ring having a small diameter. Accordingly, the formation of the annular groove is difficult and the rigidity of the shock absorbing ring is reduced by the formation of the annular groove.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a mounting device for a disk-shaped rotating tool which can reduce the vibrations during the operation of the tool with a simple structure.

In accordance with an aspect of the present invention, there is provided a device for mounting a disk-shaped rotating tool having a grinding surface on the outer circumferential portion thereof to an output shaft of an electric rotary machine, the inner circumferential portion of the disk-shaped rotating tool having a first annular retaining groove formed on at least a surface opposed to the electric rotary machine, the device including a first ringlike cushioning member fitted in the first annular retaining groove; a first holding member provided on one side of the disk-shaped rotating tool and fixed to the output shaft of the electric rotary machine; and a second holding member fixed to the first holding member so as to come into pressure contact with the first ringlike cushioning member from the other side of the disk-shaped rotating tool, thereby holding the disk-shaped rotating tool in cooperation with the first holding member.

Preferably, the disk-shaped rotating tool has a second annular retaining groove formed on another surface opposite to the surface opposed to the electric rotary machine; the device further including a second ring-like cushioning member fitted in the second annular retaining groove and pressed on the disk-shaped rotating tool by the first holding member. Preferably, the first and second annular retaining grooves are formed by corrugating the inner circumferential portion of the disk-shaped rotating tool.

Preferably, the output shaft has a seating surface formed at the base end portion thereof and a screw shaft extending axially outside from the seating surface; the first holding member has a cylindrical portion having an inner circumference formed with an internally threaded portion engaged with the screw shaft and an outer circumference formed with an externally threaded portion near one end surface abutting against the seating surface of the output shaft, the outer circumference of the cylindrical portion being integrally formed with an engaging projection for relatively nonrotatably engaging the inner circumferential portion of the disk-shaped rotating tool; and the second holding member has an inner circumference formed with an internally threaded portion engaged with the externally threaded portion of the cylindrical portion of the first holding member.

The above and other objects, features and advantages of the present invention and the manner of realizing them will become more apparent, and the invention itself will best be understood from a study of the following description and appended claims with reference to the attached drawings showing some preferred embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical sectional view of a first preferred embodiment of the present invention;

FIG. 2 is a cross section taken along the line II-II in FIG. 1;

FIG. 3 is a vertical sectional view of a second preferred embodiment of the present invention; and

FIG. 4 is a vertical sectional view showing an essential part of a third preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Some preferred embodiments of the present invention will now be described in detail with reference to the drawings. Referring to FIG. 1, there is shown a first preferred embodiment of the present invention, wherein reference numeral 10 denotes a case of an electric rotary machine such as a disk grinder. An output shaft 11 of the electric rotary machine projects from the case 10. The base end portion of the output shaft 11 is stepped to form a seating surface 11 a, and a small-diameter screw shaft 12 projects from the seating surface 11 a.

The present invention provides a device for mounting a disk-shaped rotating tool 15 such as a grinding disk through a pair of first and second holding members 21 and 28 to the output shaft 11 of the electric rotary machine. In this preferred embodiment, the disk-shaped rotating tool 15 is provided by a grinding disk. The grinding disk 15 is composed of a base plate 16 formed from a steel plate and super-hard abrasive grains fixed to the outer surface (right side surface) of the outer circumferential portion of the base plate 16. This outer circumferential portion of the base plate 16 to which the abrasive grains are fixed is formed as a grinding surface 17. The inner circumferential portion of the base plate 16 is bent toward the inside (left side) of the electric rotary machine so as to form a trapezoidal cross section as shown in FIG. 1.

The top surface of this trapezoidal inner circumferential portion of the base plate 16 is formed as an inner circumferential wall 16 a. The inner circumferential wall 16 a is corrugated by a press to form a first annular retaining groove 18 a and a second annular retaining groove 18 b. The first annular retaining groove 18 a has a depth such that a first ringlike cushioning member 30 a formed from an O ring is fitted in the groove 18 a so as to be exposed therefrom. Similarly, the second annular retaining groove 18 b has a depth such that a second ringlike cushioning member 30 b formed from an 0 ring is fitted in the groove 18 b so as to be exposed therefrom.

The inner circumferential portion of the base plate 16 is formed with a spline-shaped center hole 19. In the first preferred embodiment shown in FIG. 1, the inner circumferential wall 16 a of the base plate 16 is corrugated at one radial position. In contrast thereto, FIG. 3 shows a second preferred embodiment of the present invention, wherein the inner circumferential wall 16 a of the base plate 16 is corrugated at two radial positions radially spaced a predetermined amount to form a first annular retaining groove 18 a having a large diameter on the left side surface of the inner circumferential wall 16 a and a second annular retaining groove 18 b having a small diameter on the right side surface of the inner circumferential wall 16 a.

Both of the first holding member 21 and the second holding member 28 are formed of metal such as stainless steel. The first holding member 21 has a large-diameter flange portion 22 and a cylindrical portion 23 formed integrally with the flange portion 22 and projecting leftward therefrom. The flange portion 22 has a diameter corresponding to the diameter of the outer side surface (right side surface) of the inner circumferential wall 16 a of the base plate 16. The outer side surface (right side surface) of the flange portion 22 is formed with four operation holes 22 a for engagement of an operation tool (not shown), wherein these four operation holes 22 a are spaced from each other in the circumferential direction of the flange portion 22. The outer circumference of the base portion (right portion) of the cylindrical portion 23 is formed with three engaging projections 24 as spline teeth adapted to engage the spline grooves of the center hole 19 of the grinding disk 15. The axial length of each engaging projection 24 is preferably set slightly larger than the axial width of the inner circumferential wall 16 a of the grinding disk 15. Further, the outer circumference of the left portion of the cylindrical portion 23 is formed with an externally threaded portion 25 axially adjacent to the engaging projections 24.

The second holding member 28 has a diameter corresponding to the diameter of the inner side surface (left side surface) of the inner circumferential wall 16 a of the base plate 16. The inner circumference of the second holding member 28 is formed with an internally threaded portion 28 a adapted to engage the externally threaded portion 25 of the cylindrical portion 23 of the first holding member 21. Further, the end of the second holding member 28 is formed with a tool engaging portion 28 b having opposite flat surfaces for engaging a tool such as a wrench.

The operation of the mounting device according to the first preferred embodiment mentioned above will now be described. The first ringlike cushioning member 30 a and the second ringlike cushioning member 30 b are respectively fitted into or opposed to the first annular retaining groove 18 a and the second annular retaining groove 18 b of the inner circumferential wall 16 a of the grinding disk 15. In this condition, the cylindrical portion 23 of the first holding member 21 is inserted through the center hole 19 of the grinding disk 15 so that the engaging projections 24 of the cylindrical portion 23 come into engagement with the spline grooves of the center hole 19. Thereafter, the internally threaded portion 28 a of the second holding member 28 is engaged with the externally threaded portion 25 of the first holding member 21 until the right side surface (outer side surface) of the second holding member 28 comes into pressure contact with the left side surface of each engaging projection 24.

As a result, the first ringlike cushioning member 30 a and the second ringlike cushioning member 30 b are respectively pressed against the left side surface and right side surface of the inner circumferential wall 16 a of the grinding disk 15 by the first holding member 21 and the second holding member 28, and these cushioning members 30 a and 30 b are elastically deformed by a predetermined amount. Thus, the grinding disk 15 and the first and second holding members 21 and 28 are assembled as a unit in the condition where the grinding disk 15 is sandwiched under pressure by the first and second ringlike cushioning members 30 a and 30 b. Thereafter, the cylindrical portion 23 of the first holding member 21 is threadedly engaged with the output shaft 11 of the electric rotary machine until the left end surface of the cylindrical portion 23 comes into abutment against the seating surface 11 a of the output shaft 11. In this manner, the grinding disk 15 can be mounted quickly and accurately to the output shaft 11 of the electric rotary machine.

Referring next to FIG. 4, there is shown a vertical sectional view of an essential part showing a third preferred embodiment of the present invention. As similar to the first preferred embodiment, an inner circumferential wall 16 a of a base plate 16 of a grinding disk 15 is held by a first holding member 21 and a second holding member 28. In this preferred embodiment, a part of the inner circumferential wall 16 a is annularly removed to form a first annular retaining groove 18 a on the left side surface of the inner circumferential wall 16 a of the base plate 16, and a part of the flange portion 22 of the first holding member 21 is annularly removed to form a second annular retaining groove 22 b on the left side surface of the flange portion 22. A first ringlike cushioning member 30 a is engaged with the first annular retaining groove 18 a, and a second ring-like cushioning member 30 b is engaged with the second annular retaining groove 22 b. In this preferred embodiment, all of the first annular retaining groove 18 a, the second annular retaining groove 22 b, the first ring-like cushioning member 30 a, and the second ringlike cushioning member 30 b have the same diameter.

In operation, the first ringlike cushioning member 30 a is engaged into the first annular retaining groove 18 a of the inner circumferential wall 16 a of the grinding disk 15 so as to be partially exposed, and the second ringlike cushioning member 30 b is engaged into the second annular retaining groove 22 b formed on the left side surface of the flange portion 22 of the first holding member 21 so as to be partially exposed. In this condition, the cylindrical portion 23 of the first holding member 21 is inserted through the center hole 19 of the grinding disk 15 so that the engaging projections 24 of the cylindrical portion 23 come into engagement with the spline grooves of the center hole 19. Thereafter, the internally threaded portion 28 a of the second holding member 28 is engaged with the externally threaded portion 25 of the first holding member 21 until the right side surface (outer side surface) of the second holding member 28 comes into pressure contact with the left side surface of each engaging projection 24.

As a result, the grinding disk 15 and the first and second holding members 21 and 28 are assembled as a unit in the condition where the grinding disk 15 is sandwiched under pressure by the first and second ring-like cushioning members 30 a and 30 b. Thereafter, the cylindrical portion 23 of the first holding member 21 is threadedly engaged with the output shaft 11 of the electric rotary machine. In this manner, the grinding disk 15 can be mounted quickly and accurately to the output shaft of the electric rotary machine.

As a modification of the first preferred embodiment shown in FIG. 1, the first holding member 21 may be mounted to the grinding disk 15 so that the flange portion 22 is located on the left side of the grinding disk 15 and the cylindrical portion 23 is engaged into the center hole 19 from the left side of the grinding disk 15. Further, the second holding member 28 may be provided on the right side of the grinding disk 15 so as to engage with the externally threaded portion 25 of the cylindrical portion 23 of the first holding member 21. As another modification, the second ringlike cushioning member 30 b may be omitted to use only the first ring-like cushioning member 30 a.

The present invention is not limited to the details of the above described preferred embodiments. The scope of the invention is defined by the appended claims and all changes and modifications as fall within the equivalence of the scope of the claims are therefore to be embraced by the invention. 

1. A device for mounting a disk-shaped rotating tool having a grinding surface on the outer circumferential portion thereof to an output shaft of an electric rotary machine, the inner circumferential portion of said disk-shaped rotating tool having a first annular retaining groove formed on at least a surface opposed to said electric rotary machine, said device comprising: a first ringlike cushioning member fitted in said first annular retaining groove; a first holding member provided on one side of said disk-shaped rotating tool and fixed to said output shaft of said electric rotary machine; and a second holding member fixed to said first holding member so as to come into pressure contact with said first ringlike cushioning member from the other side of said disk-shaped rotating tool, thereby holding said disk-shaped rotating tool in cooperation with said first holding member.
 2. The device for mounting a disk-shaped rotating tool according to claim 1, wherein said disk-shaped rotating tool has a second annular retaining groove formed on another surface opposite to said surface opposed to said electric rotary machine, said device further comprising a second ring-like cushioning member fitted in said second annular retaining groove and pressed on said disk-shaped rotating tool by said first holding member.
 3. The device for mounting a disk-shaped rotating tool according to claim 2, wherein said first and second annular retaining grooves are formed by corrugating the inner circumferential portion of said disk-shaped rotating tool.
 4. The device for mounting a disk-shaped rotating tool according to claim 1, wherein: said output shaft has a seating surface formed at the base end portion thereof and a screw shaft extending axially outside from said seating surface; said first holding member has a cylindrical portion having an inner circumference formed with an internally threaded portion engaged with said screw shaft and an outer circumference formed with an externally threaded portion near one end surface abutting against said seating surface of said output shaft, the outer circumference of said cylindrical portion being integrally formed with an engaging projection for relatively nonrotatably engaging the inner circumferential portion of said disk-shaped rotating tool; and said second holding member has an inner circumference formed with an internally threaded portion engaged with said externally threaded portion of said cylindrical portion of said first holding member. 